His stint as secretary of state for energy and climate change certainly gives him the greenest track record of all the main party leaders, where he demonstrated a genuine understanding of the massive threats the planet faces and the need for urgent action. His 18-month tenure oversaw significant progress.

The Climate Change Act, which set the first national legislation anywhere in the world to cut emissions and for which Friends of the Earth led the campaign, was probably the Labour government's biggest environmental success.

The initial proposal was weak, with inadequate targets based on outdated science and with key sectors like aviation and shipping not included. The battle to improve these flaws was long and hard, but it was Ed who unlocked the opposition within government and produced an act with real teeth.

As leader he should stand more chance of winning such battles, and creating a platform that has the environment at its heart. But even as leader, he will have his work cut out to convince his party that a green agenda is the right agenda.

As delegates meet in Manchester this week, a look through the official conference agenda shows that, astonishingly, there is not a single session on environment or climate change. Other subjects have question and answer sessions, reports, debates – the environment simply does not feature on the main stage.

The idea that we can create jobs through environmental policies is not new – Chris Huhne last week talked of a ten-fold increase in jobs by insulating and refitting our houses to make them greener. Ed should challenge the union movement, especially with unemployment worries so prevalent, to back policies that deliver the most jobs for people – not just unionised jobs – encouraging them to fight for better quality homes and better environmental standards.

Of course, creating a low-carbon economy is even harder in the post-credit crunch world. But for all the talk of whether or how fast to cut, there has been too little vision of the future low-carbon economy, and how budget cuts will affect this. By investing in renewable power and energy efficiency we can create hundreds of thousands of new jobs and business opportunities, reduce our reliance on fossil fuels, slash energy bills and make the UK a world leader in tackling climate change.

A green Labour party would also win back votes from Liberal Democrats, who have long prided themselves on their environmentalism, but find themselves disillusioned with the policies coming forward. And if Ed, the unions and the wider Labour movement push the message that job creation, improved housing and reduced fuel bills arise from a shift to a low-carbon economy, it could carry real weight in the Labour heartlands, too.